[skywhopper]

The full time signature is arbitrary, and partially related to how the notes are written. It's wrong to put too much weight on "6/8" vs "3/4" per se. There are conventions that have developed in western music as to which time signature matches which natural beat pattern, but there's nothing _inherent_ in the time signatures that's important.

Instead, I find it useful to think about combinations and layers of twos and threes. So the different being talked about in this article is about whether the beat pattern is more of three groups of two, or two groups of three. Convention has mapped those, typically, to 3/4 and 6/8 respectively, but again that's entirely arbitrary.

Likewise 9/8 time is usually three groups of three. 4/4 is two groups of two (though the second two often have slightly less emphasis, whereas 2/4 time is just single groupings of two). 7/8 is a group of three and two groups of two (could be 2-2-3, or 3-2-2, or 2-3-2). 5/4 or 5/8 is a group of two and a group of three.

But ultimately time signatures are just a convenient way to hint at the beat pattern expected, and to give a framework in which to write the musical notation. The actual _music_ is not so easily transcribed.

[jballanc]

One of my favorite songs for helping to explain the importance and differences between time signatures is "Question!" by System of a Down (https://www.youtube.com/watch?v=ENBv2i88g6Y). The intro is 9/8 (as a 3-2-2-2 grouping), followed by a section in 5/4. The verses are the same 9/8, except for regular jumps to 6/8 (during the phrase "Are you dreaming?"). The chorus is 6/4, with repeats of the same 5/4 section from the intro. The bridge is a mash-up of the 5/4 again with jumps between 9/8 and 3/4 and the outro is 4/4 back to a final 9/8 section.

It's not always easy to pick out what specific signature is being played at every point in the song, but the "suspended" feeling of hanging beats as the signature changes is very obvious.

[soperj]

Can you explain what the difference between /4 and /8 are? like for example, what is the difference between 9/8 and 9/4? I've made something up that has an 11 time signature, 2-3-3-3(or 3-3-2-3), but how do I know if it's 11/8 or 11/4?

[x3n0ph3n3]

It only indicates which note symbol is the beat unit. /4 means that each quarter note gets the beat, while /8 means that each eighth note gets the beat. 3/4 means there are 3 quarter notes of time, while 6/8 means there are 6 eighth notes of time. This might help: https://en.wikipedia.org/wiki/Note_value

[bonzini]

You don't. However, in general faster tempo has a lower denominator (in classical music at least, and more rarely in jazz).

For example, a 2/2 tempo with 100 BPM is easier to "manage" than a 4/4 tempo with 200 BPM, and they are the same as each 2/2 beat corresponds to two 4/4 beats. So a "Presto" or "Prestissimo" will often be written as 2/2, with half the BPM that it would have in 4/4. Likewise, a 6/4 is usually faster than a 6/8 or 12/8.